Lakes (Grosse Fuchskuhle, Grosser Stechlinsee)

We investigated freshwater oomycete diversity in two Northeast German lakes using the metabarcoding approach. Contrary to previous assumptions, Peronosporales taxa, Pythium species in particular, dominate freshwater ecosystems; challenging the notion of Saprolegniales as a dominant freshwater lineage. Lagena, traditionally associated with terrestrial habitats, was found in shoreline sediments, highlighting the overlooked role of Peronosporales in the benthos of freshwater ecosystems. Through metabarcoding and isolation techniques, we underscore the importance of reconsidering oomycete diversity and ecological functions in the transition of aquatic to terrestrial ecosystems. Our findings expand the understanding of oomycete ecology and emphasize the need for unbiased methodologies to reveal their hidden diversity and functions in natural ecosystems.